Helical Thread (conical teeth)(trapezoidal teeth)

Parametric thread designing module:

Simple parameters:
1. Major Dia
2. Pitch (linear distance/turn)
3. Tooth Angle
4. Bolt height
5. Nut Height
6. Nut Radial thickness
7. Tolerance between screw and nut

Chamfer, Hex head for bolt are optional for the user

((Please also download "hexnut.scad" for chamfered hexnut in "helical_thread.scad"))

Core calculations:
t = radius of circle (primary primitive shape)
t/n = eccentricity of twist (radius of twist) (primary is translated by this number from the origin on any one axes perpendicular to the axis of linear_extrude)

v1-v5: (simplified)
n = (2 x major_dia x pitch x tan( tooth_angle/2 )) - 1
t = major_dia/2 x n/(n+1)

v6: (generalised)
n = (major_dia x (1 - cos( 180*pitch )) x tan( tooth_angle/2 )) - 1
t = major_dia/2 x n/( n+1 )

Generalised formula allows for a smoother tooth profile and accurate tooth angle

v7: